1. Field of the Invention
The present invention relates to an electrophotographic image printing apparatus for forming an image using a liquid developer by an electrophotographic technology. More particularly, the present invention relates to an electrophotographic printing apparatus equipped with an exhaust treating apparatus for treating an exhaust containing a vapor of a carrier solvent generated in an apparatus by use of a liquid developer.
2. Related Art
From the standpoint of the developers used, electrophotographic technologies are classified into those of dry development using a solid developer and those of liquid (wet) development using a liquid developer. In the conventional electrophotographic technologies, wet development is believed to be practically disadvantageous because of some substantial problems, and consequently, the field of image formation by electrophotographic technologies has been long occupied substantially by dry development.
However, electrophotography of wet development has also an advantage which can not be realized by dry development. Examples include that: since an extremely fine toner of sub-micron size can be used, high image quality can be realized; since sufficient image concentration is obtained with a small amount of toner, an economical advantage is obtained and texture corresponding to offset printing or other like printing can be realized; since a toner can be fixed to paper at relatively lower temperature, energy saving and high speed output can be realized; and the like. Based on these facts, the value of electrophotography based on wet development has been reviewed and development is in progress aiming at practical use.
Substantial problems of an electrophotographic technology based on wet development are concerned with vaporization of an organic solvent which is contained as a carrier in a developer and treatments thereof, and one of them is that an exhaust containing the vaporized organic solvent must be necessarily subjected to treatment for removal of the organic solvent, before discharging the exhaust out of the printing apparatus. This problem is regarded recently as important from the standpoints of environmental pollution and health. Moreover, even in use of safe petroleum-based synthetic solvents exhibiting no carcinogenicity (Isoper manufactured by Exxson Chemical Japan LTD., and the like) as a carrier, other problems such as uncomfortable odor of a solvent occur. Therefore, it is desirable that a solvent in the exhaust is removed before discharge as completely as possible.
In order to solve this problem, for example, Japanese Patent No. 2892643 and U.S. Pat. No. 5,737,674 disclose electrophotography systems in which an exhaust containing a solvent vapor is liquefied and removed, and the concentration of vaporized solvent in the exhaust in U.S. Pat. No. 5,737,674 is lowered by passing the exhaust through a cooling liquid to cool and condense the vapor of solvent.
However, in the case of removing the vaporized solvent from the exhaust by the above system, liquefaction does not progress sufficiently if the contact area of cooling liquid with the exhaust is small and the contact time thereof is short. Therefore, the apparatus should be so constituted, for assured removal of a solvent, that the contact area and the contact time with the exhaust are sufficiently secured. Thus, a certain volume is necessary. Moreover, measures for controlling the treating conditions such as temperature and the like are also required to be installed. Therefore, the whole dimension of an image printing apparatus has to be increased.
It is not only in the above method of the liquefaction mode but also in general methods that securing the contact area with an exhaust is necessary for assured removal of a vaporized solvent from the exhaust, and it is important for size reduction of an image printing apparatus to constitute the apparatus so as to realize sure purification of an exhaust in a space that is as small as possible.
An object of the present invention is to provide an electrophotographic printing apparatus equipped with an exhaust cleaning device which is advantageous for size reduction of the whole apparatus and has long life.
Moreover, another object of the present invention is to provide an electrophotographic printing apparatus equipped with an exhaust cleaning device which can manifest efficient purification function sufficiently and can purify an exhaust assuredly.
Still another object of the present invention is to provide an electrophotographic printing apparatus having an exhaust cleaning device which provides easy works of removal and change, and which can be made into a cartridge.
In order to achieve the above objects, an electrophotographic printing apparatus for printing an image on a print medium with use of a liquid developer which contains a liquid carrier and a toner being dispersed in the liquid carrier, according to an aspect of the present invention, comprises: an image printing system comprising a circulative imaging surface for forming a toner image from the liquid developer, and transferring the toner image from the circulative imaging surface to the print medium; a collection member which is capable of absorbing or adsorbing vapor of the liquid carriers the collection member being disposed in a place which is surrounded by the circulative imaging surface; and a vapor directing system which directs air containing the vapor of the liquid carrier vaporizing from the imaging surface to the collection member.